linux-kernel - [RFC PATCH v1 16/41] powerpc/32: Statically initialise first emergency context

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Message-Id: <f53c5fe97f52659bc6f37be9c5d6a9e9bb018106.1612864003.git.christophe.leroy@csgroup.eu>
Date:   Tue,  9 Feb 2021 09:56:40 +0000 (UTC)
From:   Christophe Leroy <christophe.leroy@...roup.eu>
To:     Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Paul Mackerras <paulus@...ba.org>,
        Michael Ellerman <mpe@...erman.id.au>, npiggin@...il.com
Cc:     linux-kernel@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org
Subject: [RFC PATCH v1 16/41] powerpc/32: Statically initialise first
 emergency context

The check of the emergency context initialisation in
vmap_stack_overflow is buggy for the SMP case, as it
compares r1 with 0 while in the SMP case r1 is offseted
by the CPU id.

Instead of fixing it, just perform static initialisation
of the first emergency context.

Signed-off-by: Christophe Leroy <christophe.leroy@...roup.eu>
---
 arch/powerpc/kernel/head_32.h  | 6 +-----
 arch/powerpc/kernel/setup_32.c | 2 +-
 2 files changed, 2 insertions(+), 6 deletions(-)

diff --git a/arch/powerpc/kernel/head_32.h b/arch/powerpc/kernel/head_32.h
index 88b02bd91e8e..15c6fc7cbbf5 100644
--- a/arch/powerpc/kernel/head_32.h
+++ b/arch/powerpc/kernel/head_32.h
@@ -205,11 +205,7 @@
 	lis	r1, emergency_ctx@ha
 #endif
 	lwz	r1, emergency_ctx@l(r1)
-	cmpwi	cr1, r1, 0
-	bne	cr1, 1f
-	lis	r1, init_thread_union@ha
-	addi	r1, r1, init_thread_union@l
-1:	addi	r1, r1, THREAD_SIZE - INT_FRAME_SIZE
+	addi	r1, r1, THREAD_SIZE - INT_FRAME_SIZE
 	EXCEPTION_PROLOG_2
 	SAVE_NVGPRS(r11)
 	addi	r3, r1, STACK_FRAME_OVERHEAD
diff --git a/arch/powerpc/kernel/setup_32.c b/arch/powerpc/kernel/setup_32.c
index 8ba49a6bf515..d7c1f92152af 100644
--- a/arch/powerpc/kernel/setup_32.c
+++ b/arch/powerpc/kernel/setup_32.c
@@ -164,7 +164,7 @@ void __init irqstack_early_init(void)
 }
 
 #ifdef CONFIG_VMAP_STACK
-void *emergency_ctx[NR_CPUS] __ro_after_init;
+void *emergency_ctx[NR_CPUS] __ro_after_init = {[0] = &init_stack};
 
 void __init emergency_stack_init(void)
 {
-- 
2.25.0